The present invention relates to composite machine tools capable of performing both turning process and rotating-tool process with one tool spindle. More particularly, the invention relates to a tool spindle fixing device for fixing the tool spindle to the tool headstock for the turning process.
There have been available hitherto composite machine tools, such as composite lathes, in which with a rotating tool fitted to a tool spindle rotatably supported to a tool headstock, boring, milling or other rotating-tool process can be achieved by driving the tool spindle into rotation, and in which with the tool spindle fixed to the tool headstock and with a turning tool fitted to the tool spindle, turning process can be achieved by driving a workpiece into turning.
In this type of composite machine tool, there is a need for a tool spindle fixing device which is enabled to securely fix the tool spindle to the tool headstock and to easily undo the fixing. As such a tool spindle fixing device, there has conventionally been provided one in which clamping recess portions are provided at 0.degree. and 180.degree. positions on the outer peripheral surface of the tool spindle and the tool spindle is fixed to the tool headstock by inserting a lock rod in the recess portion with oil pressure (see Japanese Patent Publication HEI 7-49164).
However, in the conventional method in which the lock rod is inserted into the recess portion of the outer circumferential surface of the tool spindle, the tool spindle could not be given sufficient clamping rigidity, and this insufficient rigidity would adversely affect particularly deep cutting processes, and also adversely affect the finished surface roughness and the like in the finish process, as problems. Further, the method is not enough satisfactory also in terms of the positioning accuracy in the rotational direction of the tool spindle.